重点讲解：
1. specialize in 专门从事；专门经营；专门研究；专攻；
He specialized in treatment of cancer patients.
他是治疗癌症病人的专家u~hdHsApvU8*2REUj]*Z。
2. slow down (使)放慢；
The body's metabolism is slowed down by extreme cold.
严寒可以使身体新陈代谢的速度下降~(D~)Yy39tx。
3. teem with 充满，充斥(人或动物)；
For most of the year, the area is teeming with tourists.
一年中大部分时间里，这个地区游人如织KLw+3VoW@cYAQyTImyQ。
4. respond to 应对；作出回应；作出反应；
The animals were conditioned to respond to auditory stimuli.
经过训练，那些动物对声音形成了条件反射na#d(ig|LO。